Field of the Invention
The present invention relates to a composition for application to hair in the manner of a hair tonic, which, upon application to the scalp, activates melanocytes of the radix pili and improves synthesis of melanin, thereby preventing graying of the hair and restoring grayed hair to its natural color.
Graying of the hair is a universal aging phenomena, while hair dyes are commonly used to dye grayed hair, the use of such dyes is troublesome and sometimes causes side-effects such as rash. Therefore, many users find hair dyes to be an unsatisfactory solution. There has thus been a great need for developing a pharmaceutical agent or a cosmetic composition for hair capable of essentially preventing graying of the hair and restoring grayed hair to its natural color.
Heretofore, there have been developed various kinds of drugs for activating the radix pili and promoting the growth of hair. On the other hand, there have been reported only a few cosmetic compositions for preventing graying of the hair and restoring grayed hair to its natural color (see, for instance, Japanese Patent Un-examined Publication (KOKAI) Nos. 60-174705, 61-165310, 62-45527, 62-63509 and 62-63510). Moreover, the reported techniques suffer from various disadvantages such as low effectiveness, low stability of the active components and insufficient safety.
The composition disclosed in Japanese Patent Unexamined Publication No. 60-174705 employs vitamin D.sub.3 and derivatives thereof. However, the cosmetic agent is incomplete in the following points:
(i) It is difficult to form the vitamin D.sub.3 and its derivatives into cosmetic preparations since they are extremely unstable in the air and easily undergo oxidation, so that the cosmetic agent cannot be expected to provide sufficient effect when applied as external preparation;
(ii) Vitamin D.sub.3 and the derivatives thereof tend to cause side-effects such as hypervitaminosis D or hypercalcemia (anorexia, vomiting, constipation, disponderal, degrowth and the like) and, therefore, there has been some doubt about safety.
Consequently, the cosmetic compositions disclosed in the above-mentioned Un-examined Publications are of little practical use.